The invention relates to valves in general, and more particularly to improvements in valves of the type wherein a valving element is mounted on and is movable by a reciprocable stem toward and from a position of sealing engagement with a seat in the interior of a valve housing or body. Still more particularly, the invention relates to improvements in valves of the type wherein the seat in the interior of the housing has a seat area which is inclined with reference to the axis of the stem, and the sealing face which surrounds the seat area is tapered and forms part (particularly an oblique strip-shaped part) of a conical surface.
German Pat. No. 546,464 discloses a valve wherein the seat area makes an oblique angle with the axis of a pipe in which the valve seat is used. The seat area is an oblique section through a circular cone, and the valving element is a conical frustum which is coaxially secured to the stem and is provided with means for preventing it from rotating relative to the housing. The passage through the housing of the patented valve is designed with a view to offer a minimum of resistance to the flow of fluid. The sealing effect of the valving element is not entirely satisfactory, and this is believed to be attributable to oblique setting of the seat area as well as to insufficient surface pressure upon those parts of the sealing face which are located in the plane including the axis of the stem and the axis of the pipe.
European patent application No. 0 109 626 discloses a diaphragm valve wherein the diaphragm cooperates with a seat which is placed at an oblique angle to the axis of the pipe. The valving element is attached to and is held by the diaphragm in requisite position with reference to the seat in the housing of the valve. A stem in the upper part of the housing is arranged to act indirectly upon the valving element by way of force transmitting means. The valve of this patent application acts not unlike a butterfly valve in that the valving element bears upon that part of the sealing face which is nearest to the top portion of the housing and is pivoted by the stem about such part between an open and a closed or sealing position. Proper functioning of the valving element is ensured by the diaphragm to which the valving element is secured. The conical valving element is subjected to one-sided stresses in the region of the sealing face nearest to the apex of the conical surface of which the sealing face is a part. Such one-sided engagement leads to insufficient surface pressures upon the slightly stressed portion or portions of the sealing face and/or to excessive surface pressures upon the strongly stressed portion or portions of the sealing face. In either event, the sealing action is problematic and unreliable, even if the valve is designed to furnish a so-called soft sealing action.